This invention relates to self-priming vertical pump systems and more particularly to an improved priming valve structure suitable for use in a self-priming vertical liquid pump system.
Self-priming liquid pumping systems are known, and an example of a widely used system of that type is illustrated in U.S. Pat. No. 3,370,604, which is owned in common by the assignee of the present invention. As there shown, a pump is positioned so that its suction inlet line is submerged in a suction chamber and the discharge line from the pump includes a check valve to prevent reverse flow through the discharge line back to the pump when suction is lost. A priming valve is positioned in the discharge line between the pump discharge and the check valve. The column of liquid between the priming valve and the check valve serves as the priming liquid, and the flow thereof back to the suction chamber is controlled by the priming valve. Heretofore, the priming valve structure in most common use was a spring-biased, poppet-type valve to which a suitable piston was secured in order to permit control of the priming valve by means of pressure from the pump discharge, which is conveyed through a conduit that extends into the discharge stream to sense the loss of priming by means of the decrease in pump output flow. The structure arrangement as briefly described hereinabove is somewhat complicated, and it is desirable to provide a system having a simpler structure in order both to facilitate manufacture and to minimize operational problems.